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3. Acoustic Analysis with COMET FEA VIBRATION ANALYSIS
Generate structural model
Run FEA program
Compute surface velocities
6. Concern Determination of sub-system (panel) contribution to the noise
Use panel acoustic contribution analysis
Associates the vibration of a panel to noise
Transfer function
Identify the type of contribution
Negative, Positive, Neutral
Make design changes
7. Physical Interpretation
9. Experimental Data Numerical determination of vibration data is limited to less than 200 Hz
Use of experimental data allows the analysis to be carried at higher frequencies - 600 Hz
COMET allows import of experimental data
Used successfully by a major automobile company
Sport utility vehicle
Weight reduction of 10 lb.
Reduction in sound level of 2 dB
Development of vehicle for Asian-Pacific region
Weight reduction of 1.3 lb.
Sound level reduction of 6 dB
10. Summary Identification of solutions not intuitively obvious
PACA provides a systematic process for noise reduction
Can be combined with experimental data
Numerical determination of vibration data is limited to less than 200 Hz
Use of experimental data allows the analysis to be performed at higher frequencies - 600 Hz
COMET allows import of experimental data
Used successfully by a major automobile manufacturer
12. Porous Media Material utilizes multiple phenomena to minimize reflected or transmitted sound energy
solid phase (the structure of the material)
fluid phase (the fluid fills the holes)
interactive between the above
Primarily used to dissipate energy
damping (viscous, structural, thermal)
Examples of porous materials
Glass fiber, Mineral wool, Partially open or open cells foams
Typical applications
Mufflers and ducts
Vehicle sound insulation
Aerospace structure sound insulation
Seals
13. Foam sandwiched by aluminum panel and air on both sides
Boundary condition
free panel edge condition
impedance + velocity on one end
impedance on the other end
impedance =
Double Panel TL
14. Double Panel TL Unbounded connection between foam and aluminum panel
Good correlation between theoretical (infinite plate) and SAFE results
Infinite plate theory applicable
15. Effect of Bond One of the plates is bonded to foam
Poor correlation between theoretical (infinite plate) and SAFE results
Good correlation between SAFE and experimental results
Usage of glue increases stiffness - increase in TL
16. Summary Models Sound Propagation
Poroelastic, fluid, structural and solid domains
Coupled and Uncoupled
2D, 3D, Axi-symmetric
Frequency response, Modal Analysis
Provides a powerful tool for the design of optimal modern noise control treatments
Used in headliners, seats, carpets, trim lining, panel damping, aircraft skin insulation, wall insulation, enclosure liners, etc.
18. Concern Objective
Perform many design iterations by rapidly determining acoustic characteristics
Analysis Aim
Associate a single parameter with each design
Computational Procedure
Vibrational characteristic from FEA, Test, NAH
Acoustic analysis using enhanced Rayleigh method Important Criteria
Not actual sound level
Variation of sound level from one design to another
19. Analysis Process Identify the frequency range of interest
Compute structural modes
Select number of frequencies in the vicinity of the structural mode
For each frequency
Get surface velocity from structural analysis
Compute sound power
Enhanced Rayleigh Method
20. Design Iteration Compute sound power for the mode
Add sound power for each frequency
Compute sound power for the system
Add power for all modes
Make design changes
Panel acoustic contribution analysis
Sensitivity analysis
Iterate until desired solution is obtained
Perform the final analysis using standard methodology
e.g. BEM, Test
21. Allows the study of design variations rapidly
Vibrational characteristics determined using FEA, Test, NAH, etc.
Acoustic characteristics computed using enhanced Rayleigh Method
Definition of a single parameter permits objective comparison of designs
Summary
23. Concern Duct system
Source
Termination
Path between source and termination
Acoustic performance depends on source-path interaction
Insertion Loss
Difference between SPL at reference point with and without path element (muffler)
Transmission Loss
24. Boundary Element Cutaway Exploded View of 7-Zone Muffler Muffler Model
25. Sound Field
26. Facilitates Sub-system modeling
Computes important acoustical quantities
Sound pressure
Sound intensity
Sound power
Transmission loss
Effect of mean-flow is easily incorporated Summary
28. CAT/COMET Interface Bringing tools to product development process
Completely integrated process
Designer should not have to leave familiar CATIA interface
Use powerful mesh creation of CATIA
Use all analysis capabilities of COMET
29. Analysis Process - I Noise caused by the vibration of structure
Define geometry (transmission housing)
ANMESH
Define vibration = Specification of surface velocities
Test or FEA structural analysis
ANPHYSIC+LOAD
30. Analysis Process - II Define locations at which results (I.e. sound pressure) are desired
Single point or group of points
ANMESH
Define material properties of acoustic domain
Density and speed of sound
ANPHYSIC+PROPERTY
31. Analysis Process - III Set analysis parameters
Frequency of analysis
ANMANAGE+ANALYSIS
Solve acoustic problem using COMET
Display results (acoustic characteristics)
Surface of the domain and/or within the domain
COMET/Vision
32. Summary
Completely integrated process
Available to analysts and designers
Import FEA results from ELFINI, ANSYS, NASTRAN, ABAQUS, COSMOS
Import test data from I-DEAS, CADA-X
Use powerful mesh creation of CATIA
Use all analysis capabilities of COMET
Post Processing Options
CATIA or COMET/Vision
34. Tire Noise
35. Concern
Characteristics
Many potential noise sources
Complex interactions
Difficult to model accurately
Goals
Identify the noise source
Predict the sound field
Predict influence of design changes
36. Nearfield Acoustic Holography Forward problem
Vibrating structure causes sound = Known sound source
Source is not always easy to determine
Inverse problem - Source identification
37. Traditional and COMET NAH Traditional NAH
Models plane sources
Measurement surface is plane
Reconstruction surface is mostly plane
COMET NAH
Models arbitrary 3D sources
Arbitrary measurement surface
Reconstruction on arbitrary 3D surface
38. Acoustic Pressure at Measurement Surface Sound pressure at measurement surface
Location and number of microphones depend on the frequency
NAH identifies the source
39. Source Identification
40. Environmental Modification
41. Next Generation NAH
Presently applied to exterior problems
NAH for interior acoustic at AAC is funded by NASA
Develop NAH for source identification inside aircraft
Verification using NRL experimental data inside aircraft
Next generation of COMET NAH extends the source identification capability to interior noise analysis
42. Summary
Allows flexible measurement layout
plane, three-dimensional
Allows source identification in complex three-dimensional geometry
Allows mixed measurement data
pressure as well as velocity
Reconstruction at measurement surface is easily verified
Effect of design modification is easily studied
44. Easy-to-Use Interface “Written by users for users”
Icons call management panels
Logical step by step process
Easy to learn and operate
ANSYS, ABAQUS, Hypermesh, I-DEAS, CADA-X, COSMOS, NASTRAN and PATRAN datafiles translated
45. COMET Service & Support AAC’s goal is to support solving acoustic problems, not simply software like some competitors
Responsive and practical technical support for real solutions to your problems
Years of experience in automotive, aerospace, heavy equipment, etc...
46. COMET Evolution - I 1994 Version 1.0 Basic (Uncoupled) BEA Module
Advanced (Coupled) BEA Module
Acoustic FEA Module Vision (GUI) Module
Version 2.0 Spherical and plane wave sources
Version 2.1 Restart capability, Structural damping
1995 Version 2.2 Direct out-of-core solver, Sensitivity analysis, Panel contribution analysis
Version 3.0 Frequency matrix interpolation, Acoustic holography, (CHIEF) - overdetermined system analysis, unique exterior solution for direct
47. COMET Evolution - II 1996 Version 3.1 Iterative solver, Discontinuous impedance, Reverberant analysis, Test data correlation
1997 Version 3.2 Windows NT Version UNIQUE - interior solution for indirect
1998 Version 4.0 SAFE Module
Mean flow, Indirect out-of-core solver, Rayleigh Integral, Transient Analysis, CAT/COMET Module
48. COMET Modules Basic Acoustic Boundary Element Analysis
Advanced Acoustic Boundary Element Analysis
Acoustic Finite Element Analysis
SAFE - Structural Acoustic Foam Engineering (New)
SAOpt - Structural Acoustic Optimization (1999)
COMET Integration with CATIA - Separate Module (New)
COMET/Vision
49. COMET Advantages SAFE superior in capabilities to any other package
Nearfield Acoustics Holography capabilities not available anywhere else
All software written by AAC
Consistent interface
Fully supported
No need to load or reload modules
Written by users for users
Thoroughly tested in engineering service before release
50. Partial Customer List 3M Corporation
Bell Helicopter
Boeing
Denso
Donaldson Company
DuPont
Ford Motor Company
Harman-Motive, Inc.
Hyundai Motors
Ibaraki NEC Company, Ltd
Isuzu Motors, Ltd.
Komatsu, Ltd.
Lear Corporation
Lockheed Martin Meritor Automotive
NASA
Nippon Sharyo, Ltd.
Onan Corporation
Prince/JCI
Raytheon Aircraft Company
Rieter Automotive
Roush Anatrol, Inc.
Samsung Advanced Industrial Technology
Siemens
Sound Alliance
Thona
Vickers, Inc.
52. Partners and Affiliations
Over $2 Million in Funding from NASA
Leading U.S. developer of acoustic software
Dassault partner for acoustics integration with CATIA
University Affiliations
Purdue University, California Institute
of Technology, Iowa State University, Georgia Institute of Technology, University of Michigan
54. Automated Analysis Corporation Regional offices near major business centers: Detroit, Chicago & London
Experience and customers in automotive, aerospace and industrial markets (about half in automotive)
ISO 9002 Registration
Long-standing and PREFERRED supplier to major corporations such as Chrysler, Ford, General Motors, and Caterpillar
55. COMET Offers the SolutionsYou Need Provides tools for practical acoustics
Offers state-of-the-art Solution Methods
Models complex and large applications
Generates fast and accurate solutions
User friendly - You don’t need to spend hours learning the software
Best support in the industry - We solve acoustic problems
Available through purchase or lease
56. Sound Field
57. Worldwide Distributors Australia
LEAP Ltd.
Benelux
FEM-Consult
Denmark
Unicus Eng.
France
ADDL
Germany
CAD-FEM
58. CAT/COMET Interface Bringing tools to product development process
Completely integrated process
Designer should not have to leave familiar CATIA interface
Use powerful mesh creation of CATIA
Use all analysis capabilities of COMET